Such systems are known, for example, from U.S. Pat. No. 4,295,833 or German publication DE-A1 40 39 425 and are employed, for example, in motor boats which exhibit high output and are difficult to steer without the hydraulic power assist. At the same time, the principle of force-balance is utilized, wherein, when the controller is actuated, not only is a torque exerted on the controlling mechanism by way of the existing mechanical connection of the core of the Bowden cable, but also a pressure medium connection is also simultaneously steered to or from the respective desired working chamber of the operating cylinder. Thus, the steering force exerted at the controller or the steering wheel is intensified in the requisite direction. The control valve is operated by means of the resulting deformation of the Bowden cable. When, following completed adjustment of the control mechanism, the deformation of the Bowden cable is cancelled again by way of the controller, the control valve returns into its central position, and adjustment of the control mechanism is thus concluded again. One particular example of actuating a controller is the manual operation of a steering wheel or the like.
One drawback of the known systems of the aforementioned kind is based in particular on the fact that such power steering systems represent closed control circuits, which tend to vibrate a lot owing to unavoidable tolerances or play in the Bowden cable, the bolts, and the like, a feature that can cause problems while steering.